A cell cycle is a process in which a cell produced by a cell division undergoes another cell division to produce a new cell. Of the cell cycle, a phase during which mitosis takes place is called an M phase. Generally, the M phase completes in approximately one hour. An interval between one M phase and another M phase is called an interphase during which cell growth as well as biosynthesis and/or metabolism of a substance occur. The interphase can be further divided into a G1 phase, an S phase, and a G2 phase. In the S phase, DNA replication takes place. The G1 phase is a phase between the M phase and the S phase, and the G2 phase is a phase between the S phase and the M phase.
As a method for analyzing a specific phase of the cell cycle (G1 phase, S phase, G2 phase, or M phase), a method using a BrdU label is known. In specific, the method includes: causing a BrdU to be taken into a cell for a given period; and subsequently, carrying out immunohistochemistry by using an anti-BrdU antibody. However, with the method, it is impossible to carry out observation in real-time. There is also known a method using cell synchronization and a biochemical model. With the method, however, it is impossible to carry out real-time observation.
As a method for visualizing a specific phase of the cell cycle, there is a method using the G2M cell cycle phase marker (G″ MCCPM) (Amersham Bioscience K.K). Because the method uses promoter activity of cyclin, there is a problem in that transformation by gene introduction is remarkably influenced depending on how a transgene is integrated into a chromosome. Further, because the G1 phase is not visualized, (i) it is difficult to track a cell cycle, and (ii) a contrast is unclear.